Powder coating is a technique of coating a metallic article with paint or a similar substance. The paint is sprayed in dry powder form onto the article through a spray gun. The gun charges the powder particles with static charge such that they are attracted to the metal. The article is then passed into an oven, where the powder coating melts to form a flat coating on the article.
Spraying articles in this way results in a considerable amount of powder missing the article (so called overspray) and settling in the enclosure or booth in which the article is being sprayed. It is therefore desirable to recover this material for re-spraying.
Moreover, it is important that this material is recovered from the enclosure or booth when the colour of material to be sprayed is changed, otherwise cross contamination of colours of material will occur.
Conventionally, recovery of such material is done by either sucking the excess powder into an airline, or alternatively by blowing the powder with an airline into a collecting chamber. These techniques have the drawbacks of causing the powder to become airborne and thus difficult to recover. Moreover airborne powder coat material presents both health and environmental hazards.
Further, using such airlines to collect overspray tends to increase the static charge of the particles, and hence their affinity to the walls of the enclosure and other metal items thereby increasing the difficulty of their recovery.